Heat treatment method and apparatus

ABSTRACT

The invention is a method of and apparatus for in-situ heat treatment for re-solutionizing β-phase in sensitized aluminum-magnesium alloy structures and, in particular, a method of and apparatus for in-situ heat treatment for re-solutionizing β-phase in sensitized aluminum-magnesium alloy structures comprising naval vessels. The invention also relates to a method for maximizing the absorption of radiant energy on a substrate. The invention also relates to an apparatus for securing a heat treatment device to a substrate having an irregular surface.

RELATED APPLICATIONS

This application claims the benefit of commonly owned U.S. Provisionalpatent application 62/418,150 filed on 4 Nov. 2016, and commonly ownedU.S. Provisional patent application 62/451,662, filed on 28 Jan. 2017.This application is related to commonly owned U.S. Provisional patentapplication 62/360,372, filed 9 Jul. 2016. The heater support device ofthis invention is similar to the support device in commonly owned U.S.patent application Ser. No. 13/561,032, filed on 28 Jul. 2012. Thisapplication incorporates by reference the disclosure of the followingcommonly US patent applications: 62/418,150 filed on 4 Nov. 2016,62/451,662, filed on 28 Jan. 2017, 62/360,372, filed on 9 Jul. 2016 and13/561,032, filed on 28 Jul. 2012.

GOVERNMENT SUPPORT

Not applicable.

SEQUENCE LISTING

Not applicable.

FIELD OF THE INVENTION

The present invention relates generally to the field of localized heattreatment of sensitized metallic compounds and, in particular, to thein-situ de-sensitization heat treatment of sensitized aluminum-magnesiumalloys in naval vessels. The present invention also relates to a methodfor maximizing the absorption of infrared energy on a target. Thepresent invention also relates to an apparatus for heat treating asubstrate having an irregular surface.

BACKGROUND

Aluminum has been used in the construction of naval vessels for morethan a century. Experimental small craft were constructed of aluminum aslong ago as the 1890's and, at that time, further use seemed promising.The first sizable craft constructed of aluminum was the sloop-riggedyacht Vendenesse, built at St. Denis in France in 1892. Aluminum platewas used for the shell plating, decks and bulkheads, although theframes, keel and stringers were steel. Within four months after launch,corrosion was observed over 20 square meters (˜200 square feet) of herbottom, where the bottom paint had failed. Corrosion was a continuingproblem for the Vendenesse. The first use of aluminum in the UnitedStates for a sizable craft occurred in 1895 when Herrshoff designed andbuilt the America's Cup yacht Defender which was to be the pride ofAmerican technology. The side shell plating and some of the frames wereof an aluminum-nickel alloy. The portion of the Defender below thewaterline was bronze, as were the rivets for the aluminum portions. Thiscombination of aluminum with bronze led to rapid corrosion of thealuminum but not before the Cup was won by Defender. The experience withthese vessels was not promising, leading Scientific American in anarticle published in 1894 to state that this experience “does notpresent a very encouraging prospect for the introduction of aluminumboats.”¹ ¹NTIS-PB2009101032; Aluminum Structure Design and FabricationGuide; Sielski, R. A.; 796 pages; 2007

Aluminum was first used in the U.S. Navy for some topside fittings forthe torpedo boats intended for the battleship USS Maine. Thesestanchions, sockets and decklight frames quickly corroded and werereplaced with steel. A similar experiment with the same results was madewith the torpedo boats Foote, Rodgers, and Winslow, which were built inBaltimore between 1895 and 1898. The first aluminum deckhouses for U.S.Navy ships were for the torpedo boats Dahlgren and Craven, which weredesigned and built by Bath Iron Works in 1898. Possibly, the use ofaluminum for the hulls by French yards interested the Bath Iron Works,and they used this new technology. However, the aluminum in these boatsevidently fared no better than it had in other applications, foraluminum was not used again in structural applications for forty years.

In the 1930s, lightweight topside structure was becoming important fordestroyers. In 1935, aluminum was reintroduced to deckhouse and was usedextensively for many other nonstructural purposes, including furnitureand joiner bulkheads. With the DD-409 class, designed in 1936, came thegreatest use of aluminum for exposed deckhouse structure. Plating wasmixed, some of aluminum, some of mild steel, with the framing of mildsteel. This application of aluminum plate was apparently successful,because the next class designed, the DD-423, used aluminum for platingthroughout the entire deckhouse, except where thick steel was used forfragment protection.

Design of deckhouse structure became rather standardized with mild steeltransverse frames spaced 21 inches supporting aluminum plating that was4.8 mm ( 3/16 inches) thick everywhere except in way of gun blast, whereit was 6.3 mm (¼ inches) thick. The next major design, the Fletcher(DD-445) class destroyers, used this configuration from the beginning ofthe class in 1940. However, with the onset of World War II, all uses ofaluminum except for aircraft came under careful scrutiny because ofshortages, and the use of aluminum in Navy ships was temporarilydiscontinued. The DD-445 class was thus a mixture of steel and aluminum.

With the USS Gearing (DD-692) and USS Sommer (DD-710) class destroyers,riveted aluminum came back, being used for about half of the deckhousesides and decks, although the transversely framed stiffeners were weldedsteel. Following the war, the development of aluminum welding had aneffect, and in 1948 the new destroyer leaders, the USS Mitcher (DL-2)class had aluminum deckhouses that were entirely welded, including thetransversely oriented frames. From about 1953 on, all new U.S. Navycombatants (destroyers, destroyer escorts, frigates and cruisers) hadaluminum for the majority of their deckhouses. In addition, aluminum isused for the deckhouse in landing ships, and for the islands of aircraftcarriers and amphibious assault ships.

The use of aluminum for the hulls of high-speed merchant vessels beganin the 1990s with increased construction of high-speed ferries. Thesevessels have become so technologically advanced that they have surpassedthe capabilities of many naval vessels; many navies today are adaptingderivatives of these high speed vessels to combatant craft.

The U.S. Navy is using 5XXX aluminum alloys as a critical constructionmaterial in the design and construction of state-of-the-art Navy ships.As noted above, aluminum had long been used in the construction of navalvessels. In order to maximize the stability and, in some cases, speed ofnaval vessels, aluminum-magnesium [5XXX] alloys have been used toconstruct ship superstructures. More recently, the current U.S. Navyshipbuilding plan is to grow the size of the fleet with significantaluminum structural components to approximately 170 vessels by 2040,including 32 Littoral Combat Ships [LCS], 20 Future Frigates [FF], 22Guided Missile Cruisers [CG], 12 Aircraft Carriers [CVN], 11 Joint HighSpeed Vessels [JHSV], and 73 Ship to Shore Connectors [SSC] to replacethe 91 Landing Craft Air Cushion [LCAC] Vehicles.² ²“QuantitativeNondestructive 5XXX Aluminum Material Assessments to Reduce TotalOwnership Costs,” Dunn, Ryan, Naval Engineering Journal, March 2016,Vol. 128, No. 1, pp 23-34

The primary alloying element in 5XXX series aluminum alloys ismagnesium. During production, highly controlled heat treatments are usedto evenly distribute magnesium in the aluminum matrix. Different alloysin the 5XXX series contain different amounts of magnesium ranging from˜3.5% in 5086 to ˜4% in 5083 and up to ˜5% in 5046. These alloys arepopular for marine applications because they combine a wide range ofstrength, good forming and welding characteristics, and high resistanceto general corrosion. 5XXX alloys with greater than 3.0% magnesiumcontent may be susceptible to stress corrosion cracking [SCC]. Inservice, limitations should be placed on the amount of cold work andmaximum permissible operating temperature for the higher magnesiumcontent alloys to avoid increased susceptibility to stress corrosioncracking and intergranular corrosion [IGC]. For these reasons, suchalloys should not be used at operating temperatures greater thanapproximately 65° C. [149° F.].

Ships and vessels constructed of 5XXX aluminum alloys are susceptible toa metallurgical phenomenon known as sensitization. The evenlydistributed state of the magnesium within the Aluminum matrix isthermodynamically metastable and exposure to even mildly elevatedtemperatures for extended periods of time can cause the magnesium toform beta-phase [Mg₂Al₃] precipitates. The formation of these beta-phaseprecipitates along the grain boundaries as a connected network is calledsensitization. Welding on existing 5XXX aluminum structures that havebecome sensitized in support of repair, maintenance and/or modificationmay require specific critical welding procedures and, in some cases, theapplication of cold working technologies or wholesale materialreplacement depending on the degree of sensitization (DoS).

As noted above, sensitization is the formation of magnesium richbeta-phase precipitates at material grain boundaries as the result ofexposure to elevated temperatures for extended periods of time. Thesebeta-phase precipitates are anodic to the surrounding aluminum matrix,and when exposed to a corrosive environment, sensitized material willexperience intergranular corrosion [IGC]. When tensile stress is appliedto material that has experienced IGC, stress corrosion cracking [SCC]can result.

At a high level, the rate of sensitization is primarily a function offour factors: thermal exposure, alloy composition (% magnesium),material temper and the material grain size and microstructure. Assumingequivalent thermal exposures, tempers, grain sizes, and microstructures,5XXX aluminum alloys containing higher amounts of magnesium willsensitize faster than 5XXX aluminum alloys with lesser amounts ofmagnesium. For example, 5046 (˜5% magnesium) will sensitize faster thanan equivalent 5083 (˜4% magnesium) sample, and 5083 will sensitizefaster than an equivalent 5086 (˜3.5% magnesium) sample when exposed tothe same thermal conditions.

The beta-phase [Mg₂Al₃] precipitates contain approximately 38% magnesiumwhich is significantly higher than the aluminum matrix, which for 5456Aluminum alloy is approximately 5% magnesium. Elemental magnesium isthermodynamically less stable and kinetically more active than elementalaluminum. These characteristics make magnesium more susceptible todissolution in low and neutral pH environments. The beta-phase [Mg₂Al₃]behaves more like magnesium than aluminum and will dissolve rapidly inseawater environments. This difference in dissolution behavior, combinedwith the fact that beta-phase forms preferentially on grain boundariesduring service, leads to the preferred corrosion of those grainboundaries. In other words, these beta-phase preferential grainboundaries are susceptible to intergranular corrosion [IGC].

Stress Corrosion Cracking [SCC] will occur if a specific set of materialproperties and environmental conditions are present. As illustrated inFIG. 1, sensitized material is one of the conditions that contributes toSCC of aluminum alloys. The sensitized material then needs to be exposedto a corrosive environment and intergranular corrosion [IGC] needs toinitiate corrosion along grain boundaries. Lastly, a tensile stressneeds to be applied to the IGC affected material to form astress-corrosion crack.

Aluminum-magnesium alloys can become sensitized in different ways.Heating and holding the alloy for even a relatively short period of timeat an elevated temperature may produce the sensitized condition.However, it is not always necessary to heat to elevated temperatures toproduce the condition.

The Naval Surface Warfare Center Carderock Division [NSWCCD] has anongoing effort to predict sensitization rates of various 5XXX aluminumalloys in the fleet. As part of this effort, two sample racks holdingsix samples each were mounted on a deployed Navy vessel. The temperatureof each test specimen was measured and recorded by an attachedthermocouple every 20 minutes. The collected temperature data was fedinto a predictive model developed by NSWCCD to predict sensitizationrates for different 5XXX aluminum alloys based on the recorded thermalexposures. Based on this data it is estimated that recrystallized 5083aluminum alloy will reach sensitization levels above 25 mg/cm² afterapproximately 7 to 10 years of normal operating fleet exposure and 5456aluminum alloy is estimated to become sensitized after approximately 4years of normal operating fleet exposure. The 25 mg/cm² test resultquoted above was obtained using the industry standard Nitric Acid MassLoss Test (hereinafter “NAMLT”). The U.S. Navy considers 5XXX alloyswhich have a NAMLT test result above 25 mg/cm² to be sensitized.

Ships and vessels with aluminum superstructures made from 5XXX aluminumalloys have experienced cracking due to the effects of corrosion.Surface ship structures made of 5456 and/or 5083 aluminum will becomesensitized from long-term [4-10 years] exposure to normal fleetoperating conditions. In addition, heat from welding processes, forexample Friction welding or Gas Metal Arc [GMA welding], used in shipfabrication and repair may also contribute to the sensitization of theseship structures. Once the ship superstructure has become sensitized, itis more prone to intergranular corrosion [IGC] and also to stresscorrosion cracking [SCC].

The importance of implementing innovative approaches to reduce totalownership costs associated with the repair, maintenance, andmodernization of vessels constructed using 5XXX aluminum alloys is bestexemplified by the problems and significant increases in total ownershipcosts associated with the repair of a significant number ofsensitization and fatigue related superstructure cracks across the22-ship Ticonderoga class guided missile cruisers. The high cost ofaluminum crack repair and significant number of CG superstructure cracksin addition to the difficulties associated with working on sensitizedaluminum has added several hundred million dollars to the totalownership costs of the CG class ships. With an additional 20 years ofservice life remaining for many of the CG class ships, it isconservative to estimate that stress corrosion cracking and thedifficulties associated with performing work on sensitized aluminum willcontinue to significantly increase total ownership costs.

BRIEF SUMMARY OF THE INVENTION

Once portions of ship structure made from 5XXX alloys have becomesensitized it was not thought that this condition was easily reversible.The normal practice to deal with this situation was, often, wholesalereplacement of the sensitized aluminum. However, it has been discoveredthat it is possible to de-sensitize these portions of ship structurein-situ by re-dissolving the beta-phase into the alloy matrix via theproper type of anneal heat treatment. Note the teachings of Kramer etal., in U.S. Pat. No. 9,394,596. This de-sensitization process issimilar to the types of mill stabilization heat treatments used for manyyears in aluminum production. Once an area of the ship structure hasbeen determined to be sensitized, an in-situ heat treatment using aportable heater is applied to de-sensitize the affected area. One of thedisadvantages of this type of treatment is that it tends to anneal thestructure. Because the 5456 aluminum-magnesium alloy commonly used innaval ship construction derives its strength from work hardening, thetreated, annealed plate is softer than, for example, the H116 or H321marine grade plate. Thus, close control of the anneal heat treatment iscritical.

This invention is a method for in-situ de-Sensitization of a 5XXX alloystructure by applying a localized heat treatment. The heat treatment issimilar to a mill stabilization treatment used to reverse sensitizationand to restore corrosion resistance and shape fixability in existingAluminum-magnesium products. Such a treatment is disclosed in Zhao etal. U.S. Pat. No. 6,248,193 B1 which reference teaches heating acontinuously cast and rolled aluminum-magnesium alloy sheet with from3%-6% magnesium to a temperature of 240° C. to 340° C. and holding thattemperature for one hour or more. As taught in Zhao et al. this heat andhold treatment followed by a slow cooling ensures that magnesiumsegregated through continuous casting may be reliably precipitated inthe form of particles along the grain boundaries. Of course, in a millsetting, such heat treatments are fairly easily carried out. Doing adesensitization heat treatment on an existing structure such as a shipis another matter entirely.

Another portion of the invention is a new method for more efficient heattransfer during the in-situ heat treatment process for aluminum, othermetals and of non-metallic compounds. One of the heat sources envisionedfor use in providing heat to the sensitized aluminum substrate is aninfrared emitter. This heat source is well-known in the art. What is newis the concept of tuning the frequency of the infrared emitter to matchthe absorption spectrum of the material being heated. For example, withthe sensitized aluminum of the current invention, the aluminum reflectsover 90% of the infrared energy impacting it over a wide range ofimpacting energy wavelengths. Except if the frequency of the impactingradiation is in the 600-900 nm range, there is a pronounced dip in theenergy reflected. At approximately 825 nm wavelength of impactinginfrared radiation, the aluminum only reflects about 86% of the energyimpacting it. In other words, the aluminum absorbs more of the impactedenergy if the energy is coming in at these frequencies. This means thatthe in-situ heat treatment may be performed more efficiently.

Another way to achieve a more efficient heat transfer during the in-situheat treatment process for sensitized aluminum, other metals and ofnon-metallic compounds is to coat the sensitized aluminum, other metalor non-metallic compound with a coating which will absorb more of theinfrared energy than the bare substrate would absorb. It is envisagedthat this coating would either be able to withstand the temperaturesinvolved and be removed at a later time, or be a sacrificial coating anddesigned to burn off during the treatment.

Another portion of the invention involves the provision of a heattreatment apparatus which is capable of applying a closely controlledheat treatment to a substrate of interest which substrate may have anirregular surface. The apparatus comprises a support device and aheating unit. The support device supports the heating unit directly overthe substrate of interest and permits the system to be secured to onesurface of the substrate of interest in a removable and non-destructivemanner. The support device has legs which have securing means on thebottom thereof to secure the system to one surface of the substrate ofinterest in a releasable and non-destructible way. Normally the supportdevice will have at least three (3) legs [although there may be more orless as desired and/or necessary]. Typically, these securing meanscomprise powerful suction cups, but they may be magnetic if thesubstrate is ferrous or they could be any other suitable means to securethe device to a substrate in a releasable and non-destructible way. Thesupport device also permits the heating unit to be biased towards thesubstrate of interest. Removable, as used herein, means that the systemmay be placed upon a surface of the substrate of interest and thenremoved. The idea is that the legs permit the device to be secured toand removed from a substrate in a manner that does not damage thesubstrate. It is to be understood that not damaging the substrate maystill permit a cleaning or light abrasion of the substrate to remove aprotective coating in the area where the treatment is desired. Thesupport device also has an adjustment means that permits each leg toindependently extend/retract as necessary to accommodate a substrate ofinterest with an irregular [non-planar] surface. The legs permit thedevice to be biased against the surface and the design of the heaterassures that the surface directly under the heater will receive thecorrect treatment and the area even immediately outside the heater willreceive minimal heat. In certain applications, the heating unit will bethermally sealed against the surface.

The substrate will most often be a metal, often aluminum, and may havean irregular surface. To provide the best contact possible with such anirregular substrate, each leg of the device is independently adjustable[as noted above] in order to move the heater body closer or farther awayfrom the substrate surface. Each leg has a two stage adjustment system,a coarse adjustment and a fine adjustment. As mentioned above, thesupport device comprises means to secure the device to the substrate ofinterest and permits the device to be biased against the substrate. Thisfeature, in combination with the above mentioned independentlyadjustable legs permits the device to be used on substrates withirregular surfaces. If the means to adhere is a suction cup, it is evenpossible to removably secure the device to an vertical surface usingvacuum-powered suction cups. These are suction cups powered by air beingforced through a vacuum producing venturi closely associated with thesuction cup. Using this type of design, it has been found that thedevice can be used successfully on substrates that actually are inclinedslightly beyond the vertical.

There are several significant problems inherent in performing such aheat treatment on an existing aluminum-magnesium structure. First of allis the problem of detecting just exactly which portions of the existingstructure are sensitized and would thus need to be de-sensitized.Secondly, it is important when working on the sensitized portion of anexisting structure that the surrounding, non-sensitized areas not becomesensitized by the heat treatment applied to the sensitized areas. Thissituation can occur if the surrounding, non-sensitized areas receive toomuch heat from the de-sensitization process. Thirdly, it is important tomake sure that the de-sensitizing treatment not reduce the strength ofthe existing, sensitized structure below acceptable levels. Lastly, itis important to make sure that the structure being treated [andsurrounding structures] have the absolute minimum deformation as aresult of the de-sensitization heat treatment.

The industry standard test for determining the degree of sensitizationof aluminum-magnesium alloy structures is the NAMLT test [Nitric AcidMass Loss Test]. The NAMLT test requires cutting sample coupons fromareas of the structure that are suspected of being sensitized and thenperforming the NAMLT test on them. This test essentially destroys thesample coupons and harvesting the sample coupons leaves holes in thealuminum structure. Cutting numerous holes in the structure of a billiondollar ship is not going to win anyone a popularity contest. Since it isextremely difficult, if not outright impossible, to determinesensitization by merely looking at a suspect area, harvesting samplecoupons is definitely a hit-or-miss affair. Experience with repair ofprevious cracks on similar ships in the fleet might at least suggestwhich portions of the structure are likely to be sensitized—but this isstill a less than satisfactory method for directing sample couponharvesting. Fortunately, the recent development of the DoS-Probe [notethe article by Ryan C. Dunn (one of the inventors of this application)“Quantitative Nondestructive 5XXX Aluminum Material Assessments toReduce Total Ownership Costs,” Dunn, Ryan, Naval Engineering Journal,March 2016, Vol. 128, No. 1, pp 23-34] makes this detecting step vastlyeasier. Using a DoS-Probe to perform a non-destructive sensitizationtest of various portions of the existing structure permits a rapiddetermination of exactly which portions of the structure are sensitized.There are also other sensors which can be used to determine the degreeof sensitization [DoS] of an aluminum-magnesium structure, for examplethe microwave sensor developed by AlphaSense, Inc.

FIG. 2 ³ illustrates the effect of temperature on susceptibility ofvarious aluminum-magnesium alloys to stress corrosion cracking. Thex-axis represents the weight % of magnesium in the aluminum-magnesiumalloy. The y-axis represents temperature in °C. Area 1 is the boundaryof the sensitized range. Area 3 is the β-phase solid stability limit orthe annealed range. Area 2 is the stabilization range. A sensitizedstructure made of aluminum-magnesium alloy with ˜4 wt % magnesium [say5083 alloy] can be de-sensitized by a heat treatment which heats thestructure to a temperature of about 190° C. ³E. H. Dix, Jr., W. A.Anderson, M. B. Shumaker, “Influence of Service Temperature on theResistance of Wrought Aluminum-Magnesium Alloys to Corrosion,”CORROSION, Vol. 15, No. 2, pp. 55t-62t, February, 1959.

It is important to control the heat treatment closely to preventsurrounding non-sensitized areas from becoming sensitized by thede-sensitization treatment. This could occur, for example, if anon-sensitized area of the 4% wt magnesium structure close to thesensitized area was heated to a temperature ˜160° C. by waste heat fromthe de-sensitization treatment. FIG. 3 illustrates the forward portionof a Ticonderoga class CG cruiser. Let us say [for example] that area Aas shown in FIG. 3 represents an area of interest on the deckhouse ofthe ship made from 5083 aluminum-magnesium alloy. Let us further saythat this is an area where stress cracks were known to have been aproblem in the past. FIG. 4 is a close-up view of area A. Let us furtherassume that it has been determined that portion B of area A issensitized, but that the remaining portions of area A are notsensitized. Heat treatment of portion B to de-sensitize it, for exampleas disclosed in the above noted Kramer et al patent U.S. Pat. No.9,394,596, may require a controlled heating of portion B of area A to,say, approximately 240° C. for ˜30 minutes. It is quite possible thatother portions of area A [for example, immediately adjacent theboundaries of portion B] will be heated to approximately 160° C. becauseof the de-sensitization treatment of portion B. This could put theseportions of area A into the sensitization portion 1 as shown in FIG. 3.Thus, in de-sensitizing portion B, portions of area A could becomesensitized. Obviously, this is not a desirable outcome. In order toprevent this situation, it is known to use thermal dams to protectsurrounding areas when a particular area is being de-sensitized. Atypical thermal dam might be water-cooled or, perhaps, air-cooled. Anytype of thermal dam which is robust enough to handle the necessaryhandling and temperature issues will suffice.

It should be noted that it generally takes more time to havealuminum-magnesium alloys become sensitized than it does to desensitizethem—thus heating an area of an unsensitized or moderately sensitizedaluminum-magnesium alloy to the sensitization range [for example, Area 1in FIG. 2] for short periods of time [5-10 minutes or so] will notimpart significant amounts of sensitization, while heating a sensitizedaluminum-magnesium alloy to approximately 260° C. for a short period oftime [4 minutes or less] can cause the sensitized aluminum-magnesiumalloy to become de-sensitized.

It is also important to prevent the structure being de-sensitized [andsurrounding areas as well] from losing too much strength throughannealing. It is obvious that the use of thermal dams could be animportant tool in controlling this undesirable side effect.

Of course, it is also important to prevent the structure beingde-sensitized [and surrounding areas as well] from undesirabledeformation during a de-sensitization treatment. The use of thermal damscould also be an important tool in controlling deformation.

The heat treatment method of this invention involves an in-situ heattreatment of a sensitized area of an existing structure using a portableheating device. The gist of the invention is to use the minimum amountof heat effective to achieve the desired result for the minimum amountof time. Once the desired heat has been applied for the desired time,the heat source is turned off and the affected area is allowed toair-cool. This reduces unwanted sensitization of surrounding material,reduces unwanted annealing and undesirable deformation of the structure.Having stated these principles, minimum heat for the minimum time, itshould be recognized that there might be times where more heat than thebare minimum necessary may be desirable in order to avoid undesirablecollateral damage as will be further explained below in § [0037].

In order to achieve this treatment, a protocol is determined for thespecific aluminum-magnesium alloy comprising the sensitized structure.This protocol is determined using the relationships shown in FIG. 2. Atarget de-sensitization DoS value is determined for the sensitizedstructure. Based upon the wt % of Mg in the 5XXX aluminum-magnesiumstructure, a minimum temperature range and minimum hold time necessaryto de-sensitize the structure is determined. A portable heater [such asthat shown in FIGS. 8-17 [18] or a heater such as shown in FIGS. 1[321]-7 [38]] with any necessary thermal dams is applied to thestructure and the in-situ treatment is initiated. Once the sensitizedmaterial is in the desired temperature range and has been held there forthe desired amount of time, the application of heat is discontinued andthe structure allowed to air cool.

A heat treatment protocol with very short hold times is used tode-sensitize a sensitized structure. Once the structure has reached thedesired temperature, it is not maintained at that desired temperaturefor long periods of time. For example temperature maintenance timeperiods of 5 to 60 minutes [as stated in the aforementioned Kramer etal. patent [U.S. Pat. No. 9,394,596] are not used. This method usestemperature maintenance times in the order of 0 to 4 minutes. Forexample, it might be determined that for a particular sensitized 5XXXstructure with that the minimum temperature—minimum hold time protocolto de-sensitize the structure is 230° C., with a hold time of zero [0]minutes. The structure could then be heated to 230° C. and allowed toimmediately air-cool with essentially zero [0] minutes hold time. Thisprocess is illustrated in FIG. 5. For another sensitized 5XXX structureit might be determined that the minimum temperature-minimum hold timeprotocol is heating to 230° C. with a minimum hold time of 3 minutes.This process is illustrated in FIG. 6. For another sensitized 5XXXstructure it might be determined that the minimum temperature-hold timeprotocol is heating to 230° C. with a minimum hold time of two [2]minutes. However, it may be desirable to have a shorter hold time [i.e.less than two minutes] in this instance because of concerns over“collateral damage” to surrounding portions of the structure due tosensitization, deformation and/or annealing issues. In this instance itmay be decided to heat to a higher temperature [say 280° C. ] so that azero [0] minute hold time may be used in order to address thesecollateral damage issues. This process is illustrated in FIG. 7.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the process by which 5XXX aluminum alloy can becomesensitized and is discussed supra in paragraph [0017].

FIG. 2 illustrates the effect of temperature on the susceptibility ofvarious aluminum-magnesium alloys to stress corrosion cracking and isdiscussed supra in paragraph [0030].

FIG. 3 is a drawing of the forward portion of a Ticonderoga class CGcruiser.

FIG. 4 is a drawing of an area of interest “A” on the deckhouse of aTiconderoga class CG cruiser.

FIG. 5 illustrates a first embodiment of a process for the in situ heattreatment to de-sensitize a sensitized aluminum structure.

FIG. 6 illustrates a second embodiment of a process for the in situ heattreatment to de-sensitize a sensitized aluminum structure.

FIG. 7 illustrates a third embodiment of a process for the in situ heattreatment to de-sensitize a sensitized aluminum structure.

FIG. 8 illustrates a first embodiment of an apparatus 100 particularlyadapted to perform the processes for the in situ heat treatment tode-sensitize a sensitized aluminum structure illustrated in FIGS. 5-7.

FIG. 9 illustrates the water-cooled thermal dam portion 104 of apparatus100.

FIG. 10 illustrates a cross-section of the water-cooled thermal damportion 104 of apparatus 100 along plane C-C of FIG. 9.

FIG. 11 illustrates a cross-section of the water-cooled thermal damportion 104 of apparatus 100 along plane D-D of FIG. 9.

FIG. 12 illustrates a vortex tube.

FIG. 13 illustrates a second embodiment of an apparatus particularlyadapted to perform the processes for the in situ heat treatment tode-sensitize a sensitized aluminum structure illustrated in FIGS. 5-7.

FIG. 14 illustrates a cross-section of the thermal dam portion 104′ ofapparatus being cooled by vortex tube 120.

FIG. 15 shows an end view of a first embodiment of a heater unit for thein situ heat treatment apparatus of the invention.

FIG. 16 shows a plan view of the heater unit shown in FIG. 15.

FIG. 17 shows an end view of a second embodiment of a heater unit forthe in situ heat treatment apparatus of the invention.

FIG. 18 shows a plan view of the heater unit shown in FIG. 17.

FIG. 19 shows a side view of a third embodiment of a heater unit for thein situ heat treatment apparatus of the invention.

FIG. 20 shows a plan view of the heater unit shown in FIG. 19.

FIG. 21 illustrates a heat treatment process as performed by the heaterunit shown in FIGS. 19 and 20.

FIG. 22 also illustrates the heat treatment process performed by theheater unit shown in FIGS. 19 and 20.

FIG. 23 also illustrates the heat treatment process performed by theheater unit shown in FIGS. 19 and 20.

FIG. 24 illustrates another embodiment of the heat treatment processperformed by the heater unit shown in FIGS. 19 and 20.

FIG. 25 illustrates an Alpha sensor which gives a more or lesscontinuous readout of the degree of sensitization of an aluminum plate.

FIG. 26 illustrates a heat treatment apparatus with four independentlyadjustable mounting means.

FIG. 27 illustrates a single independently adjustable mounting means andthe fine height adjustment means of same from the heat treatmentapparatus of FIG. 24.

FIG. 28 illustrates the coarse height adjustable mounting means of theheat treatment apparatus of FIG. 24.

FIG. 29 shows an alternate embodiment of the adjustable mounting meanswhich permits removably mounting of a heating means to a non-planarsurface.

FIG. 30 is a graph illustrating a typical spectral profile for aluminumof percentage reflectance of radiation impacting the aluminum verses thewavelength of the impacting radiation.

FIG. 31 is a graph illustrating a spectral profile of percentagereflectance of radiation impacting a sample verses the wavelength of theimpacting radiation for an Ag coated sample and an Al coated sample.

FIG. 32 is a graph of the Spectral dependence of the spectral, normalabsorptivity α_(λ, n) and reflectivity ρ_(λ, n) of selected opaquematerials including an Aluminum evaporated film and black paint.

FIG. 33 shows a side elevation a first embodiment of the second heattreatment device of the invention.

FIG. 34 shows a bottom view of the device from the perspective of arrowsA in FIG. 33.

FIG. 35 shows a top or plan view of the device of FIG. 33.

FIG. 36 illustrates the heating unit of the device of FIGS. 33-35 withheat shields attached.

FIG. 37 shows a partial cross-section of the heating unit of FIG. 35.

FIG. 38 illustrates the coarse height adjustment means of the embodimentof FIGS. 33-35.

FIG. 39 illustrates a second embodiment of the second heat treatmentdevice of the invention mounted on a non-planar surface.

DETAILED DESCRIPTION OF THE INVENTION

Since FIGS. 1-7 have been discussed supra, this section begins with adescription of FIG. 8.

A heating apparatus 100 suitable for performing these processes is shownin FIG. 8. Apparatus 100 comprises a prism-shaped heater shroud 102surrounded at its lower border with a water-cooled thermal dam 104.Carrying handles 106, 106′, 106″ and 106′″ are placed at the corners ofapparatus 100 to aid in carrying and positioning apparatus 100. Powercord 110 provides any necessary electrical power to the heating elementsinside heater shroud 102.

FIG. 9 shows the water-cooled thermal dam 104 of FIG. 8. Thewater-cooled thermal dam 104 comprises solid aluminum blocks 112, 112′,112″ and 112′″ arranged in a generally rectangular fashion about thelower portion of heating shroud 102. Blocks 112, 112′, 112″ and 112′″are joined together at joints 114, 114′, 114″ and 114′″ by welding orany other suitable joining means. Internal water conduit 116 runsthrough each block 112, 112′, 112″ and 112′″. In block 112 cooling wateris fed in at inlet 118 [shown in FIG. 10], flows through the conduit 116in thermal dam 104 and exits block 112 at outlet 118′.

FIG. 10 shows a cross-section of water-cooled thermal dam 104 at planeC-C of FIG. 9. Block 112 contains an internal water pipe 116 [notillustrated in FIG. 10] which ends in outlet conduit 118′ which conduitpermits the cooling water to exit thermal dam 104 after absorbing wasteheat. FIG. 11 shows a cross-section of thermal dam 104 as shown at planeD-D of FIG. 9.

It is possible to construct thermal dam 104 with types of coolingdevices other than internal water pipes. For example air vortex tubecoolers may be used. The vortex tube was discovered in 1928 by GeorgeRanque. The device uses compressed air as a power source, has no movingparts, and produces hot air from one end and cold air from the other.The volume and temperature of these two airstreams are adjustable with avalve built into the hot air exhaust. Temperatures as low as −50° F.(−46° C.) and as high as +260° F. (127° C.) are possible. FIG. 12illustrates a vortex tube 120. Compressed air is fed into vortex tube120 at inlet nozzle 125 [usually at from 80 to 100 PSIG] and hot airflows out of outlet nozzle 123 while cold air flows out of outlet nozzle124.

A generally accepted explanation of how a vortex tube works is asfollows. Compressed air is supplied to the vortex tube and passesthrough nozzles that are tangent to an internal counterbore. Thesenozzles set the air in a vortex motion. The air may well be spinning atup to 1,000,000 rpm in this vortex. This spinning stream of air turns90° and passes down the hot tube in the form of a spinning shell,similar to a tornado. A valve at one end of the tube allows some of thehot air to escape. What does not escape, heads back down the tube as asecond vortex inside the low-pressure area of the larger vortex. Thisinner vortex loses heat to the larger vortex and exhausts through theother end as cold air.

FIG. 13 shows a heating apparatus 100′ similar to that shown in FIG. 8except the apparatus 100′ uses a thermal dam 104′ which is cooled bymultiple vortex tubes 120. Power cord 110′ provides any necessaryelectrical power. Twelve (12) vortex tube coolers are shown in FIG. 13,but the exact number of vortex tubes used will vary depending upon thespecific heating and cooling requirements encountered in the field andmore than 12 or fewer than 12 may be used as necessary. Each vortex tube120 is fed compressed air from a suitable source [not shown in FIG. 13for clarity] as indicated by the curved arrows in FIG. 13 near the lowerportions of vortex tubes 120. The warm air is exhausted at the upperportion of each vortex tube 120 while the cold air is exhausted throughthe lower portion of the tubes 120 into thermal dam 104′ as shown inFIG. 14. As noted above, this air may be at a temperature as low as −46°C. and can be quite useful for cooling purposes. Also as noted above,the air exhausted from the upper portions of tubes 120 may be attemperatures as high as ˜127° C. Rather than simply exhaust this hot airand waste the thermal energy therein, it is envisaged that this air willbe collected and used as an energy source in the heating process. Forexample, in heating apparatus 100′, hot air collection tubes 124 [notall of which are numbered in FIG. 13] extend from each vortex tube 120to a central collection plenum 126. The collected air is then passedover the material being heated by heating apparatus 100′.

FIG. 14 shows how a single vortex tube 120 would be mounted on thermaldam 104′. Cold air outlet 124 of vortex tube 120 is fastened within bore150 in thermal dam 104′. Bore 150 communicates with cooling air conduit116′ within thermal dam 104′. It is noted that cooling air conduit 116′is shown somewhat larger than water pipe 116 [of FIG. 11], however thisis explained by the different thermal capacities of water and of air.Cold air flows out of outlet 124 into and through air conduit 116′ asshown by the arrows in FIG. 14. The air flow exits through bore 152 inthe side of thermal dam 104′ after absorbing heat.

FIGS. 15 and 16 show a heater 100″ comprising a prism-shaped heatingshroud 122 without a thermal dam. Six (6) resistive wire heatingelements 126 are secured inside shroud 122 in a position where they canheat a substrate which shroud 122 is positioned upon. Obviously, othertypes of heating devices could be used to provide the heat necessary forthe inventive heat treatment process—such as induction coils or radiantheaters or any suitable heat source. It should be noted that certainapplications of this inventive method may not need a thermal dam andthat the heating shroud 122 might be used as shown herein [i.e., withoutan attached thermal dam] to perform a heat treatment according to theinventive method.

FIGS. 17 and 18 show a heater 100′ comprising a prism-shaped heatingshroud 132 without a thermal dam. Fifteen (15) radiant heating elements130 are secured to the outside of shroud 132 in a position where theycan heat a substrate which shroud 132 is positioned upon. Not all of theradiant heaters shown in FIGS. 17 and 18 have lead lines going to themfor the sake of clarity. Obviously, fifteen (15) radiant heaters 130 areshown in FIGS. 17 and 18, but the exact number of radiant heaters 130used will vary depending upon the specific heating and coolingrequirements encountered in the field and more than 15 or fewer than 15may be used as necessary and desirable. It should be noted that certainapplications of this inventive method may not need a thermal dam andthat the heating shroud 132 might be used as shown herein to perform aheat treatment [i.e., without an attached thermal dam] according to theinventive method.

FIGS. 19 and 20 show a heater 100′″ comprising a point heat source 136without a shroud or a thermal dam. Point heat source 136 is centrallypositioned on one side of plate 160. Point heat source 136 could beinfra-red, radiant, induction, a laser or any other suitable type ofpoint heat source. Point heat source 136 should be capable of beingpulsed or cycled [i.e., operated in an intermittent manner]. Point heatsource 136 is mounted on plate 160 by means of stand 138 and right anglesupport rod 137. As is illustrated in FIGS. 21 and 22, heat source 136operates as a point source of heat and is focused essentially in themiddle of plate 160 as shown in FIG. 21 by reference numeral 152. FIGS.21 and 22, will be further described below.

FIG. 23 is a plot of temperature verses distance on the sensitized 5XXXplate 160 where the β-phase in the sensitized aluminum is beingre-solutionized. Let us assume that the treatment protocol calls forheating to a temperature range of from 250° C. to 300° C. with a threeand one half (3.5) minute hold time. Point heat source 136 is used toheat substrate 160 and it is used in a pulsed or intermittentfashion—that is, it is not on all the time. The point heat source 136 isused to heat the center point 152 of the sensitized 5XXX plate 160 tobetween 250° C. and 300° C. and impinges on the center of the plate 160;however, the heat flux flows outwardly from the central point 152 asshown by the arrows in FIG. 21. As the heat flux flows away from thecenter of plate 160, the plate temperature will drop. In this example,the plate temperature at a distance approximately 4.2 inches away fromcentral point 152 will drop to 250° C. Thus the circular area G shown inFIG. 20a will be heated to between 250° C. and 300° C. Further coolingwill occur as the distance increases from central point 152 until theportion of plate 160 10 inches out from the center is only at 100° C.When the temperature in circular area G reaches 250° C. the applicationof heat is continued for the proper hold time [in this example 3.5minutes] and then the application of heat is discontinued and plate 160is allowed to air-cool back to ambient temperature.

With proper selection of the cycling of the intermittent heat source136, this situation can be maintained as long as desired with no thermaldam or other structure being necessary to keep the temperature of area Gof plate 160 between 250° C. and 300° C. and still maintain the portionof plate 160 outside of circular area H at or below 100° C. Theadvantages of this system are obvious, the pulsed or intermittent heatsource is cheaper to operate than one which is on all of the time, anddoing away with the necessity of a thermal dam eliminates most of thestructure [shroud, etc.] of the heat treatment device. This is clearly agreat simplification of the heat treatment process.

As noted above in § [0032] it generally takes more time to havealuminum-magnesium alloys become sensitized than it does to desensitizethem—thus heating an area of a unsensitized or moderately sensitizedaluminum-magnesium alloy to the sensitization range [for example, Area 1in FIG. 2] for short periods of time [5-10 minutes or so] will notimpart significant amounts of additional sensitization. Thus, in thetreatment example discussed above in §§ [0087]-[0088] even though thearea of plate 160 between circular area G and circular area H will beheated to a temperature between 250° C. and 100° C. for a short periodof time [5-10 minutes or so] it will not become sensitized.

FIG. 21 shows how the heat flux flows on treatment plate 160 when thedevice shown in FIGS. 19 and 20 is used to apply heat to plate 160. Asnoted above in §[0087] and [0088] the heat from point heat source 136impinges on plate 160 at point 152. The heat flux then flows outwardlyas shown by the arrows in FIG. 21. As also noted above, the temperatureof the treatment plate 160 decreases with distance from center point152.

FIG. 24 illustrates a second method of heat treatment according to theinvention. FIG. 24 illustrates the same basic situation and treatmentprotocol as that shown in FIG. 23. In FIG. 23 the heat source is turnedon and run intermittently until the central portion of sensitized plate160 reaches 300° C. and then the heater is shut off. The treatmentprotocol called for a temperature of 300° C. and a hold time of zero (0)minutes. In FIG. 24, a DoS sensor 168 is utilized to give a more or lesscontinuous readout of the degree of sensitization of plate 160. Thistype of reading can be done with the newly developed Alpha sensor asshown in FIG. 25. The device uses a cavity perturbation technique tonon-destructively measure the degree of sensitization [DoS] of asensitized aluminum-magnesium plate within approximately one (1) minute.The Alpha-sensor will even measure the DoS value of a coated plate. Thesensor probe 168 is connected to the hand-held electronics and controlpackage 174 by cable 170.

FIG. 24 illustrates how the Alpha sensor can be used as a feedbackcontrol for the entire heat treatment process according to theinvention. Probe 168 is emplaced on the surface of 5XXX plate 160 insidethe heating zone. Electronics and control package 172 is placed safelyoutside the heating zone and the two are connected by cable 170. Withthis type of set-up, once it has been determined that plate 160 issensitized [and this can be done by the Alpha sensor] the heat source165 can be energized and a heat treatment for re-solutionizing β-phasein sensitized aluminum can be initiated on plate 160 without determininga minimum temperature-minimum heating time protocol. A targetde-sensitization DoS value for plate 160 will need to be determined anda target treatment temperature range will also need to be determined.The control package 172 can take the DoS values from plate 160 on a moreor less continuous predetermined schedule and use these values tocontrol the heat treatment in a feedback manner When the DoS valuesmeasured by probe 168 reach the desired target level, the application ofheat can be discontinued and the plate allowed to air cool.

FIG. 26 illustrates a heat treatment device 300 with independentlyadjustable mounting means 200, 200′, 200″ and 200′″ attached to each ofthe four sides of heating device 300 and attached to thermal dam 305.The mounting means are essentially similar to those shown in commonlyowned U.S. patent application Ser. No. 13/561,032. One of theseindependently adjustable mounting means 200 is further illustrated inFIG. 27 and is described below

Base mount 312 is securely mounted to thermal dam 305 or such otherportion of heating shroud 302 as is desired in order to orient theindependently adjustable mounting means 200 as is shown in FIG. 27.Independently adjustable mounting means 200 comprises a mounting meansfor a large, bellows-type suction cup 303 powered by a coaxial venturi302 mounted to the upper portion of suction cup 303. Venturi mountassembly 308 attaches coaxial venturi 302 to height adjustment screw 304which provides a fine height adjustment for mounting means 200.

This fine height adjustment is achieved by means of adjustment nut 306which is captured in the fork 309 of adjustment screw mount 310.Adjustment nut 306 is threaded onto adjustment screw 304 [the threads onadjustment screw 304 are not shown in the drawings for clarity] but iscaptured in fork 309 of adjustment screw mount 310. Using thisconstruction, rotation of adjustment nut 306 moves adjustment screw 304upwardly or downwardly and thus moves suction cup 303, which is attachedto the lower end of screw 304, upwardly or downwardly as shown by thedouble-headed arrow next to suction cup 303. Thus suction cup 303 can bemoved up or down.

Adjustment screw mount 310 is attached to heating device 300 by leg basemount 312. The means attaching the adjustment screw mount to the legbase mount permits a coarse height adjustment of adjustment screw mount310 with respect to leg base mount 312 as will be further describedbelow in regard to FIG. 28. Adjustment screw mount 310 is shown withfive linearly spaced holes 340, 340′, 340″, 340′″ and 340′″ bored intothe right side of adjustment screw mount 310. Each hole 340, 340′, 340″,340′″ and 340′″ has a smaller perpendicular hole bored there through topermit a push pin [not shown] to be inserted into the holes. Base mount312 has a corresponding number of linearly spaced holes [not shown]bored therein. Pins 342, 342′ are removably secured in two of thecorresponding holes bored in base mount 312. Pins 342, 342′ havetransverse bores 344, 344′ bored there through. In operation, base mount312 would be assembled to adjustment screw mount 310 with pins 342, 342′being inserted into the corresponding holes in adjustment screw mount310. When assembled, the perpendicular holes in adjustment screw mount310 align with the transverse bores 344, 344′ of pins 342, 342′. Pushpins [not shown] are inserted through the aligned perpendicular holesand transverse bores 344, 344′ to secure the assembly. In order toadjust the relative position of adjustment screw mount 310 and basemount 312, the push pins would be removed, adjustment screw mount 310and base mount 312 would be separated, and pins 342, 342′ could then beinserted into different holes 340. This would give a different relativeposition between adjustment screw mount 310 and base mount 312. Inaddition, pins 342, 342′ could be removed from their holes in base mount312 and placed in other holes in base mount 312 to achieve differentrelative positioning of adjustment screw mount 310 and base mount 312.

FIG. 29 shows an alternative independently adjustable mounting means200″ for heating shroud 302′. Base mount 312′ is attached to thermal dam305′ of heater shroud 302′. Generally horizontal rod 1001 is movablymounted toleg base mount 312′. As shown by the arrows in FIG. 28a ,these rods can move up or down on leg base mounts 312′. Generallyperpendicular upper leg 1002 is attached to horizontal rod 1001 asshown. Lower leg 1003 is attached to upper legs 1002 by universal joint1004. Thus, lower leg 1003 has a large range of motion with respect toupper leg 1002. This arrangement permits suction cup assembly 1005 aconsiderable amount of movement such that it can be aligned with unevensurfaces.

When the suction cups are all properly positioned, and heating device300 secured to the sensitized portion of the structure, the air isturned on and a sizable suction drawn in each suction cup. By thesemeans the heat treatment device 300 may be held on just about any typeof surface, including a more than vertical wall, to accomplish ade-sensitization heat treatment.

Since the in situ heat treatment process of the instant invention isintended to be performed upon large structures such as portions of aTiconderoga class CG cruiser or any other vessel comprising sensitizedaluminum. With this in mind, it is clear that when performing the insitu heat treatment processes described above, a considerable amount ofheat energy must be generated by the heat-treatment apparatus,transmitted to the substrate material and then absorbed by the substratematerial—usually 5XXX aluminum. Obviously, if there is any way toimprove the heat transfer efficiency of this process, it would be a verydesirable addition to the processes described above.

When radiant energy is directed onto an aluminum surface, the aluminumsurface tends to reflect over 90% of the radiant energy impacting itover a wide range of impacting radiant energy wavelengths. This isillustrated in FIG. 30 which shows a typical aluminum spectral profileof percentage reflectance of energy verses the energy wavelength. Notethat with 250 nm wavelength radiation, the aluminum percentagereflectance is about 89%. This increases to about 92% at 500 nmwavelength radiation. In the range of wavelengths from about 1000 nm to2500 nm the percentage reflectance is about 94% to 97+%. Oddly enough,there is a pronounced dip in the percentage of reflectance in the 600 to900 nm wavelength range. As shown in FIG. 30, the percentage ofreflectance for aluminum “bottoms out” at approximately 86% at awavelength of approximately 825 nm. Obviously, to at least a limitedextend, the portion of radiant energy reflected back from an aluminumsurface depends upon the wavelength of the impacting radiation. Asdiscussed supra, this portion is greater than 90% for a wide range ofimpacting energy wavelengths, but it dips to about 86% for impactingenergy in the 825% nm wavelength. Of course, the showing of FIG. 30 alsomeans that when the impacting radiant energy has a wavelength of about825 nm the aluminum is absorbing more energy than when the impactingradiant energy has a wavelength of, say, 500 nm or 1000 nm or 2000 nm.

As shown in FIG. 31, aluminum coated substrates also show this markeddip in reflectance of radiant energy at the 600-900 nm wavelength. Thus,the radiant energy apparatus of the invention could be used on analuminum coated substrate for more efficient heat transfer. As is alsoshown in FIG. 31, Gold and Silver coated materials also show pronounceddips in reflectance depending upon the wavelength of the impactingradiant energy. Therefore, the inventive process could be used on Au orAg coated materials to achieve a more efficient heat transfer.

In view of the discussion above in paragraph [0101], it should bepossible to have a more efficient radiant energy transfer to an aluminumsubstrate if the impacting radiant energy has a wavelength in the 600 to900 nm range and even more efficiency is obtained when the impactingenergy has a wavelength of approximately 825 nm. To this end, the heattreatment apparatus used in performing the in situ heat treatmentprocesses of the instant invention would be tuned to generate radiantenergy in the wavelengths which would insure the maximum absorption ofenergy depending upon the substrate being treated. If the substrate wasaluminum, the emitter wavelength would be in the 600 to 900 nm range andmost particularly, approximately 825 nm. For other materials, theemitter wavelength would be tuned to the most favorable absorption rangefor the particular target material.

Another way to achieve more efficient energy transmission would be toadjust the radiant energy absorption of the substrate in apre-determined wavelength range of the emitter instead of fine-tuningthe emitter wavelength. For example, the substrate surface could betreated to absorb more energy in the pre-determined wavelength range ofthe emitter. One method of treatment for the substrate might be to sandor abrade the surface of the substrate. Another acceptable method fortreating might be polishing the surface of the substrate. Or, a coatingwhich has a high degree of radiant energy absorption in thepre-determined wavelength range could be applied to the substratesurface. The coating might be sacrificed during the heat treatment or itmight be selected such that it could survive the heat treatment.

FIGS. 33-35 show a first embodiment of the invention. The structure ofdevice 700 permits accurate temperature control of the local substratearea immediately under the device. Device 700 also has an attachmentmeans which permits the device to be secured to substrates with asomewhat irregular surface morphology. It is noted that device 700 isadapted to work on horizontal surfaces, sloped surfaces, verticalsurfaces, and even on surfaces that are slightly beyond vertical. It isto be understood that the means used to attach the device of FIGS. 33-35to a substrate are show as suction cups. However, if the substrate ofinterest is ferrous, magnetic means could be used in place of suctioncups. It is also possible to use a releasable adhesive means to mountthe device of FIGS. 33-35 to a substrate of interest.

FIG. 33 shows a side view of device 700 while FIG. 34 shows a bottomview of the device viewed from the direction of arrows A-A in FIG. 33.FIG. 35 shows a top or plan view of device 700. These figures will bedescribed together as they are different views of the same device withsome common components hidden in one view but visible in the other.

Device 700 comprises a base 726 which is shown with the shape of anirregular hexagon. Obviously, other shapes than an irregular hexagoncould be used, as desired and/or necessary. Base cover 732 is mounted tothe upper portion of base 726. Also mounted to base 726 are leg basemounts 712, 712′ and 712″. These leg base mounts provide the mountingmeans for the suction cup assemblies 701, 701′ and 701″. Heater mount750 is mounted to the lower portion of base 726 by multiple dowels whichare fixed to base 726 and slidably secured in heater mount 750. Three ofthese dowels 752, 754 and 756 are shown in FIG. 33. This permits theheater mount 750 to slide towards and away from base 726 in a controlledmanner while keeping heater mount 750 generally parallel to base 726.The motion of heater mount 750 is controlled by screws 722 and 722′which are rotatably fixed in heater mount 750 and threaded in base 726such that rotation of screws 722 and 722′ moves heater mount 750 awayfrom or towards the lower portion of base 726. Heating unit 600 isaffixed to the lower portion of heater mount 750. Thus, movement ofheater mount 750 towards or away from base 726 causes heating unit 600to move towards or away from base 726.

Each suction cup assembly comprises a large bellows-type pneumaticsuction cup 703, 703′ and 703″ with a coaxial venturi 702, 702′ and 702″mounted to the upper portion thereof. Venturi mount assemblies 708 [notshown in the drawings], 708′ and 708″ attach coaxial venturis 702, 702′and 702″ to adjustment screws 704 [not shown in the drawings], 704′ and704″. Elongated, threaded adjustment screws 704, 704′ and 704″ areloosely carried in a through-bore [not shown in the drawings] which runsvertically through adjustment screw mounts 710, 710′ and 710″.

Adjustment screw mounts 710, 710′ and 710″—as can be seen from FIG.33—are generally shaped as an inverted “L” with the inverted, verticalleg of the “L” mounted to leg base mounts 712, 712′ and 712′″,respectively. Each adjustment screw mount has a transverse slot 760 [notshown in the drawings], 760′ and 760″ in the horizontal portion of the“L”. Adjustment nuts 706, 706′ and 706″ which are threaded ontoelongated, threaded adjustment screws 704, 704′ and 704″, respectivelyare captured within transverse slots 760 [not shown in the drawings],760′ and 760″ to permit fine height adjustment of adjustment screws 704,704′ and 704″ with respect to the adjustment screw mounts 710, 710′ and710″. This happens because adjustment nuts 706, 706′ and 706″ arethreaded onto adjustment screws 704, 704′ and 704″, respectively, andthus have only limited horizontal movement in the plane of transverseslots 760 [not shown in the drawings], 760′ and 760″. The top and bottomof transverse slots 760 [not shown in the drawings], 760′ and 760″restrain adjustment nuts 706, 706′ and 706″ in the vertical directionsuch that rotation of an adjustment nut in one direction will move theadjustment screw it is threaded onto up [or down] with respect totransverse slots 760, 760′ and 760″ while rotation of the sameadjustment nut in the other direction will cause said adjustment screwto move in the opposite direction to the first movement. In this mannerthe device can be raised away from a substrate of interest or loweredtoward a substrate of interest. Because the motion is controlled by thethreaded connection between adjustment screws 704, 704′ and 704″ andadjustment nuts 706, 706′ and 706″ the device movement is slow and thisconnection provides a fine height adjustment means. It is noted thateach adjustment screw 704, 704′ and 704″ can be independently adjustedfor height.

Adjustment screw mounts 710, 710′ and 710″ are attached to base 726 byleg base mounts 712, 712′ and 712″. The means attaching the adjustmentscrew mounts to the leg base mounts permits a coarse height adjustmentof adjustment screw mounts 710, 710′ and 710″ with respect to the legbase mounts 712, 712′ and 712″ as will be further described below.Electrical connections 734 and 736 are provided to furnish power todevice 700 to power the heating unit 600 as described below.

The device of the invention has a means to control the temperature ofthe substrate of interest in the area in the area immediately underneaththe device. It is noted that the embodiments disclosed herein all useheating means to control the temperature of the local substrate areaimmediately beneath the device; however, it is recognized that somesituations might call for a cooling means to control these temperatures.

The temperature control features of the instant invention involve theuse of heating elements in thermal contact with the substrate ofinterest in the area directly underneath the device. The temperaturecontrol feature will be further discussed below. In addition, thisembodiment requires compressed air to power the coaxial venturiassemblies 702, 702′ and 702″ in order to provide a vacuum in suctioncup assemblies 701, 701′, 701′″.

The temperature control means for the substrate of interest is heatingunit 600. This is shown in some detail in FIGS. 34 and 36. Heating unit600 comprises a hollow shell 601 with spaced walls 602 and 604 whichhollow shell is shaped like an inverted box an open bottom. As shown inFIGS. 34 and 36 [plan views], shell 601 has the shape of a rectanglewith rounded corners. It is obvious that other geometric shapes could beused for the shape of hollow shell 601, for example, it could be squareor trapezoidal [with or without rounded corners], round, oval or anyother suitable shape, as desired. Filling the space between spaced walls602 and 604 is a continuous insulation piece 612. Inside the inner wall604 are spaced heating coils 620,620′, 620″, 620′″, 620′″ and 620′″″.Hex adjustment screws 722 and 722′ [shown in FIGS. 32 and 34] permit theheating unit 600 to be moved towards or away from base 726. Mountingposts 621 and 621′ serve to mount heating coil 620 to inner wall 604.They also provide power to heating coil 620. In like manner heatingcoils 620′, 620″, 620′″, 620′″ and 620 are mounted and powered bymounting posts 622, 622′; 623, 623′; 624, 624′; 625, 625′ and 626, 626′respectively. Flexible heat shields 650, 651, 652 and 653 are generallyrectangular pads of heat-resistant and insulative material which aredesigned to localize and limit the spread of heat applied by the heatingcoils.

A cross-section of heating unit 600 and hollow shell 601 is shown inFIG. 37. Shell 601 further comprises spaced outer wall 602 and innerwall 604 curve over at the top and are also insulated in the top area bycontinuous insulation piece 612. Spacers 606, 607, 607′ and 607″ arefastened to and run between outer wall 602 and inner wall 604. Thesespacers and others not shown in the drawings serve to maintain thedistance between inner wall 602 and outer wall 604. They pass throughthe insulation material 612. It is obvious from the above descriptionthat thermal energy from heating coils 620, 620′, 620″, 620′″, 620′″ and620 can escape out of the open bottom of hollow shell 601 to impingeupon the surface of a substrate of interest.

FIG. 38 shows the means which attaches adjustment screw mount 710 to legbase mount 712 and provides a coarse height adjustment as discussedabove. Obviously, similar means are provided to attach adjustment screwmounts 710′ and 710″ to leg base mounts 712′ and 712″. In FIG. 38adjustment screw mount 710 is shown with a proximal face 762 and adistal face 764. Five linearly spaced holes 740,740′, 740″, 740′″ and740′″ of a first diameter are bored into proximal face 762 of adjustmentscrew mount 710 at a first pre-determined spacing. Each hole 740,740′,740″, 740′″ and 740′″ has a smaller perpendicular hole 741,741′, 741″,741′″ and 741′″ bored there through to permit a push pin [not shown] tobe inserted into the holes.

In FIG. 38 leg base mount 712 is shown with a proximal face 766 and adistal face 768. Distal face 768 has a set of linearly spaced holes [notshown] bored therein at the same spacing as the first pre-determinedspacing with the holes being the same diameter as said first diameter.Pins 742, 742′ are removably secured in two of the holes in distal face768 of leg base mount 712 by pins [not shown in the drawings], threads[also not shown in the drawings] or by any other suitable means. Pins742 and 742′ have transverse bores 744 and 744′ there-through. Inoperation, leg base mount 712 would be assembled to adjustment screwmount 710 with pins 742, 742′ being inserted into corresponding holes740 and 740″ in adjustment screw mount 710. When assembled, theperpendicular holes 741 and 741″ in adjustment screw mount 710 alignwith the transverse bores 744,744′ of pins 742, 742′. Push pins [notshown] are inserted through the aligned perpendicular holes andtransverse bores 744, 744′ to secure the assembly. In order to adjustthe relative vertical position of adjustment screw mount 710 and legbase mount 712, the push pins would be removed, adjustment screw mount710 and leg base mount 712 would be separated, and pins 742 and 742′could then be inserted into different holes, for example 740′ and 740′″.This would give a different relative position between adjustment screwmount 710 and leg base mount 712. In addition, pins 742, 742′ could beremoved from their holes in leg base mount 712 and placed in other holesto achieve different relative positioning of adjustment screw mount 710and leg base mount 712.

FIG. 39 illustrates how another embodiment 800 of the device can be usedto apply heat to a non-planar surface 810. Base cover 832 is mounted tothe upper portion of base 826. Also mounted to base 826 are leg basemounts 812, 812′ and 812″. These leg base mounts provide the mountingmeans for the suction cup assemblies. The suction cup assembly and itsassociated mounting means with leg base mount 812″ is not shown in thedrawings but is substantially similar to those of suction cup assembliesfor leg base mounts 812 and 812′. Heater mount 850 is secured to thelower portion of base 826 by multiple dowels 852, 854 and 856 which arefixed to base 826 and slidably secured in heater mount 850. This permitsheater mount 850 to move towards and away from the lower portion of base826 is a controlled manner while maintaining heater mount 850 generallyparallel to base 826. The motion of heater mount 850 is controlled byhex adjustment screws 822 and 822′ which are rotatably fixed in heatermount 850 and threaded into base 826 such that rotation of screws 822and 822′ moves heater mount 850 away from or towards the lower portionof base 826. Heating unit 900 is attached to heater mount 850 and moveswith it. Thus, movement of heater mount 850 towards or away from thelower portion of base 826 causes heating unit 900 to move towards oraway from the lower portion of base 826. When the device 800 is securedto a substrate, this arrangement permits the heating unit to be movedtowards and away from the substrate of interest as will be explainedbelow.

Generally horizontal rods 801, 801′ are movably mounted toleg basemounts 812, 812′. As shown by the arrows in FIG. 39, these rods can moveup or down on leg base mounts 812, 812′. Generally perpendicular upperlegs 802, 802′ are attached to horizontal rods 801, 801′ as shown. Lowerlegs 803, 803′ are attached to upper legs 802,802′ by universal joints804,804′. Thus, lower legs 803, 803′ have a large range of motion withrespect to upper legs 802, 802′. This arrangement permits suction cupassemblies 805, 805′ a considerable amount of movement such that theycan be aligned with uneven surfaces as shown.

Although not shown in FIG. 39 a horizontal rod 801″ is movably mountedon leg base mount 812″. A generally perpendicular upper leg 802″ [notshown in FIG. 39] is mounted to horizontal rod 801″. A lower leg 803″[not shown in FIG. 39] is mounted to upper leg 802″ by a universal joint804″ [not shown in FIG. 39]. This arrangement permits suction cupassembly 805″ [not shown in FIG. 39] a considerable amount of movementsuch that it can be aligned with uneven surfaces. It is noted that thesuction cup assemblies 703′, 703″ shown for device 700 in FIG. 33 arerather large bellows-type suction cup assemblies. The construction ofthe bellows-type suction cup itself permits attachment of the suctioncup to rather uneven surfaces because of the flexibility of thebellows-type suction cup. Thus, if suction cup assemblies 805, 805′ and805″ are bellows-type suction cups, the very construction of the suctioncup coupled with the flexible mounting means shown in FIG. 39 willpermit attachment of device 800 to a wide range of non-planar surfaces.

Once the device 800 has been secured to substrate 810, heating means 900can be adjusted as described above such that it is thermally sealed tosubstrate 810. This is achieved by moving heater mount 850 by means ofhex adjustment screws 822, 822′ such that the attached heating means 900is biased towards surface 810. The heating means 900 is lowered towardssubstrate 810 until flexible heat shields 951, 952, 953 and 954 [heatshield 954 is not shown in FIG. 39] are deformed as shown in FIG.38—thus sealing heating means 900 against surface 810. Heating coils620, 620′, 620″ etc. are energized and the portion of substrate 810immediately under the heating unit 900 can be subjected to a controlledapplication of heat. The heat shields 951, 952, 953 and 954 permit theheat to be applied to a very controlled area such that portions ofsubstrate 810 not directly underneath heating means 900 do not suffersignificantly elevated temperature.

No timer or control means is shown for device 700 or for device 800 butit is noted that the art is replete with such control means which aresmall enough to be mounted on either device 700 or device 800. Either anopen loop or closed loop type of heater control means could be utilizedto control heating means 600 or 900. It is also possible to simply usean external timer in conjunction with a power on/off switch to controlthe heat application based upon calibration testing for the particularsubstrate being treated.

The above-described embodiments are merely illustrative of theprinciples of the invention. Those skilled in the art may make variousmodifications and changes, which will embody the principles of theinvention and fall within the spirit and scope thereof.

Obviously, this invention is primarily concerned with the treatment of5XXX aluminum alloy structures. However, the equipment described abovecould be used to heat most any type of substrate where heat treatmentwas desired. For example, other metals could be treated; Gold [Au] orSilver [Ag] for example. Other metals and even non-metallic materialscan also be treated with the processes and apparatus of the invention.

The above-described embodiments are merely illustrative of theprinciples of the invention. Those skilled in the art may make variousmodifications and changes, which will embody the principles of theinvention and fall within the spirit and scope thereof.

1. A method of in-situ heat treatment for de-sensitizing all orpredetermined portions of a sensitized 5XXX aluminum-magnesium alloystructure comprising the steps of: defining a treatment area within saidsensitized structure; determining a goal temperature for said treatmentarea; determining a goal heat maintenance time for said treatment area;temporarily attaching a portable heat treatment device to said treatmentarea; turning said heat treatment device on and applying heat to saidtreatment area to achieve said goal temperature within said treatmentarea; maintaining said goal temperature for said predetermined heatmaintenance time; turning said treatment device off so that it is nolonger applying heat to said treatment area; and, allowing saidtreatment area of said structure to air-cool back to ambienttemperature.
 2. The method of claim 1 wherein said defined treatmentarea is only a portion of the total area of said 5XXX aluminum-magnesiumalloy structure and wherein boundary areas surround said definedtreatment area, and further wherein said boundary areas are cooledduring the heat treatment process to regulate the temperature of saidboundary areas.
 3. The method of claim 1 wherein said goal temperatureis between 100° C. and 350° C.
 4. The method of claim 1 wherein saidgoal heat maintenance time is 4 minutes or less.
 5. A method of in-situheat treatment for de-sensitizing all or predetermined portions of asensitized 5XXX aluminum-magnesium alloy structure comprising the stepsof: defining a treatment area within said sensitized structure;determining a de-sensitization degree of sensitization [DoS] targetvalue for said treatment area; determining a goal temperature for saidtreatment area; temporarily attaching a portable heat treatment deviceto said treatment area, with said heat treatment device comprising aheat source and at least the sensor portion of a degree of sensitization[DoS] sensor being mounted inside the heat treatment device with saidtemporarily attaching step further comprising placing said DoS sensor incontact with said treatment area; determining the starting DoS of saidtreatment area; turning said heat treatment device on and applying heatto said treatment area to achieve said goal temperature within saidtreatment area; monitoring the DoS of said treatment area on apredetermined schedule during said heat applying step; turning said heattreatment device off so that it is no longer applying heat to saidtreatment area when the monitored DoS of said treatment area reaches thepredetermined de-sensitization DoS value for said treatment area; and,allowing said treatment area to air-cool back to ambient temperature. 6.The method of claim 5 wherein said heat treatment device furthercomprises a feedback control means which means controls said DoSmonitoring and which feedback control means further comprises a means toturn said heat treatment device on or off in accord with the value ofsaid DoS monitoring.
 7. A device for in-situ heat treatment tode-sensitize a sensitized 5XXX aluminum-magnesium alloy structurecomprising: a heat source; a prism-shaped, shroud containing said heatsource with said shroud having an open bottom and a closed top; athermal dam mounted to and surrounding said open bottom of said shroud.8. The device of claim 7 wherein at least one handle is mounted to saidthermal dam.
 9. The device of claim 7 wherein said thermal dam iswater-cooled.
 10. The device of claim 9 further comprising water inletand outlet means on said thermal dam.
 11. The device of claim 7 whereinsaid thermal dam is made of aluminum.
 12. The device of claim 7 whereinsaid thermal dam is provided with at least one vortex tube air coolerwith said vortex tube air cooler further comprising a compressed airinlet, a cold air outlet and a hot air exhaust.
 13. The device of claim12 wherein said hot air exhaust of said at least one vortex tube aircooler is channeled inside the shroud to aid in heating said structure.14. The device of claim 7 wherein said heat source comprises at leastone radiant wire heating coil.
 15. The device of claim 7 wherein saidheat source comprises at least one radiant heater.
 16. The device ofclaim 7 further comprising at least two, independently adjustablemounting means secured to said thermal dam which means will secure saidin-situ heat treatment device to a substrate of indefinite size.
 17. Thedevice of claim 16 wherein each of said at least two independentlyadjustable mounting means further comprises a base mount secured to saidthermal dam and an adjustment screw mount removably mounted to said basemount.
 18. The device of claim 17 wherein each of said at least twoindependently adjustable mounting means further comprises alongitudinal, threaded adjustment screw movably mounted in saidadjustment screw mount.
 19. The device of claim 18 wherein each of saidat least two independently adjustable mounting means further comprisesan adjustment nut threaded onto said adjustment screw and retainedwithin said adjustment screw mount such that turning said adjustment nutin one direction moves said adjustment screw in one longitudinaldirection and turning said adjustment nut in the other direction movessaid adjustment screw in the opposite longitudinal direction.
 20. Theapparatus of claim 18 wherein each said adjustment screw mount has aproximal side and a distal side with each said adjustment screw beingloosely received in a through-bore in said distal side of saidadjustment screw mount, with said through-bore being interrupted by atransverse slot; a threaded adjustment nut rotatably mounted in saidtransverse slot in such a manner that it can be manually rotated by anoperator; and, each said adjustment screw being threaded through theadjustment nut mounted in said transverse slot wherein rotation of saidadjustment nut in one direction causes each said adjustment screw tomove up through said through-bore and wherein rotation of saidadjustment screw in the other direction causes each said adjustmentscrew to move downwardly through said through-bore.
 21. The device ofclaim 16 wherein said at least two, independently adjustable mountingmeans further comprise at least one leg base mount secured to saidthermal dam with each leg base mount having a proximal side and a distalside; an attachment arm mounted generally perpendicular to the distalside of each leg base mount; means permitting said attachment arm to bemoved along said leg base mount in a first direction perpendicular tosaid attachment arm; said means also permitting said attachment arm tobe moved in a second direction perpendicular to said attachment arm andin opposition to said first direction; a leg mounted generallyperpendicular to each said attachment arm, with said leg comprisingfirst and second segments; and, joining means joining said first andsecond leg segments, said joining means further comprising a lockinguniversal joint to permit the angle between said first and said secondleg segments to be widely varied, and to lock said segments in positionwhen said angle has been set.
 22. The device of claim 21 wherein saidsecond leg segment carries a suction cup means at the end of said legsegment remote from said joining means.
 23. The device of claim 22wherein said suction cup further comprises a bellows-type pneumaticsuction cup.
 24. A method of in-situ heat treatment for de-sensitizing apredetermined portion of a 5XXX aluminum-magnesium alloy structure whichpredetermined portion is sensitized and which predetermined portion hasat least one non-sensitized boundary area(s) bordering upon saidsensitized predetermined portion, without adversely affecting said atleast one non-sensitized boundary area(s) surrounding said predeterminedportion, and without using any external cooling device to cool saidnon-sensitized boundary areas, comprising the steps of: determining ade-sensitization degree of sensitization [DoS] target value for saidpredetermined portion; determining a goal temperature for saidpredetermined portion; determining a maximum allowable temperature forsaid at least one non-sensitized boundary area(s); providing a portable,point source heat treatment device, with said portable, point sourceheat treatment device comprising a heat source which can be operatedintermittently and providing an associated control means to operate saidheat source in an intermittent manner; temporarily attaching saidportable, point source heat treatment device to said structure such thatsaid point source heat treatment device is placed over saidpredetermined portion and can apply heat to the part of saidpredetermined portion which is immediately under said point source heattreatment device; providing a degree of sensitization [DoS] sensorcomprising a sensor probe and an electronics and control package;temporarily attaching at least the sensor probe of said DoS sensor tosaid predetermined portion; using said DoS sensor to determine thestarting DoS of said predetermined portion; turning said point sourceheat treatment device on and applying heat to said part of saidpredetermined portion immediately under said point source heat treatmentdevice to achieve and maintain said predetermined goal temperaturewithin said part of said predetermined portion immediately below saidpoint source heat treatment device; monitoring the DoS of saidpredetermined portion on a predetermined schedule during said heatapplying step; turning said point source heat treatment device off sothat it is no longer applying heat to said predetermined portion whenthe monitored DoS of said predetermined portion reaches thepredetermined de-sensitization DoS value for said predetermined portion;and, allowing said predetermined portion to air-cool back to ambienttemperature.
 25. A method of in-situ heat treatment for de-sensitizing apredetermined portion of a 5XXX aluminum-magnesium alloy structure whichpredetermined portion is sensitized and which predetermined portion hasat least one non-sensitized boundary area(s) bordering upon saidsensitized predetermined portion, without adversely affecting said atleast one non-sensitized boundary area(s) surrounding said predeterminedportion, and without using any external cooling device to cool saidnon-sensitized boundary areas, comprising the steps of: determining agoal temperature for said predetermined portion; determining a goal heatmaintenance time for said predetermined area; providing a portable,point source heat treatment device, with said portable, point sourceheat treatment device comprising a heat source which can be operatedintermittently and providing an associated control means to operate saidheat source in an intermittent manner; temporarily attaching saidportable, point source heat treatment device to said structure such thatsaid point source heat treatment device is placed over saidpredetermined portion and can apply heat to the part of saidpredetermined portion which is immediately under said point source heattreatment device; turning said point source heat treatment device on andapplying heat to said part of said predetermined portion immediatelyunder said point source heat treatment device to achieve said goaltemperature; maintaining said predetermined goal temperature within saidpart of said predetermined portion immediately below said point sourceheat treatment device for the predetermined goal heat maintenance time;turning said point source heat treatment device off so that it is nolonger applying heat to said predetermined portion; and, allowing saidpredetermined portion to air-cool back to ambient temperature.
 26. Amethod of heat treating a substrate comprising; providing a substrate tobe heat treated having a known reflectance-radiation wavelength spectralprofile with a pre-determined minimum reflectance wavelength range;providing a radiant energy emitter which can emit radiant energy over awide range of wavelengths and, in particular, can provide radiant energyin the pre-determined minimum reflectance wavelength range of thesubstrate; directing radiant energy onto a surface of the substrate bycausing the radiant energy emitter to emit radiant energy in thepre-determined minimum reflectance wavelength range of the substrate;and, thus, maximizing the heat transfer between the radiant energyemitter and the substrate.
 27. A method of heat treating a substratecomprising; providing a substrate to be heat treated; providing aradiant energy emitter which can emit radiant energy over apre-determined range of wavelengths; coating the substrate with acoating which will increase the radiant energy absorption of thesubstrate in the pre-determined range of wavelengths emitted by theradiant energy emitter, directing radiant energy onto a surface of thesubstrate by causing the radiant energy emitter to emit radiant energyin the pre-determined range of wavelengths; and, thus, maximizing theheat transfer between the radiant energy emitter and the substrate. 28.A method of heat treating a substrate comprising: providing a substrateto be heat treated with said substrate having a pre-determined treatmentsurface; providing a radiant energy emitter which can emit radiantenergy over a pre-determined range of wavelengths; treating thetreatment surface of said substrate in such a way so as to increase theradiant energy absorption of the treatment surface of said substrate inthe pre-determined range of wavelengths emitted by the radiant energyemitter; directing radiant energy onto said treatment surface of saidsubstrate by causing said radiant energy emitter to emit radiant energyin the pre-determined range of wavelengths; and, thus, maximizing theheat transfer between the radiant energy emitter and the substrate. 29.The method of claim 28 wherein said treating step further comprisessanding said pre-determined treatment surface of said substrate.
 30. Themethod of claim 28 wherein said treating step further comprisespolishing said pre-determined treatment surface of said substrate. 31.The method of claim 28 wherein said treating step further comprisescoating said pre-determined treatment surface of said substrate with acoating which coating has a high radiant energy absorption in thepre-determined wavelength range of wavelengths emitted by the radiantenergy emitter.